A recent lawsuit by three British citizens may upset Brexit’s agreed upon timeline and disrupt the outcome of the decision to leave the EU. Britain’s High Court ruled in favor of the lawsuit on Thursday, agreeing that Parliament gets a say in the decision to leave the European Union.

Complications…A recent lawsuit by British citizens could disrupt the planned British Exit from the EU. Photo-by: BBC.com

This means that Theresa May, the Prime Minister of Britain, can’t trigger the process of leaving the EU on her own; she must first seek approval from Parliament. This new development comes in the wake of the June 23rd vote to leave the EU, which passed with a 52-48% margin. In order for the UK to actually leave the EU, it must invoke an agreement called Article 50 of the Lisbon Treaty, which would give both sides two years to agree to the terms of the separation.

Prime Minister May has stated that she intends to initiate the process by the end of March 2017, which would put the actual exit from the EU sometime near the end of the summer of 2019.

However, this lawsuit could throw a wrench into that plan.

The suit, filed by Deir Dos Santos, Charlie Mullins, and Gina Miller, (a hairdresser, a plumber, and an investment manager, respectively), challenges the right of Prime Minster May to trigger Article 50 without obtaining backing from the Parliament. They maintain that only Parliament can make the decision to leave the EU, but clarify that they are not trying to overturn the decision made by the public.

“We are all leavers now,” Miller says to BBC Radio Four.

“It is about any government, any prime minister, in the future being able to take away people’s rights without consulting Parliament,” Miller said. “We cannot have a democracy like that. That isn’t a democracy, that is verging on dictatorship,” she continued.

Disarray…Prime Minister Theresa May had planned to begin the steps for leaving the EU by the end of March, but that could change if the Supreme Court upholds the lawsuit. Photo-by: Kirsty Wigglesworth/Associated Press

The government has appealed the decision of the High Court to favor the case, and will present their case to the British Supreme Court next month.

If the appeal fails, they will likely have to bring forth an act of Parliament, which would mean getting approval from both the MPs (Members of Parliament), and the House of Lords. And while the general consensus is that they will ultimately support the decision to leave the EU (based on the results of the June 23rd referendum), involving the full parliamentary process could spur attempts to amend legislation or add in details, further complicating the process.

So while the lawsuit doesn’t seem to be aimed at stopping a British Exit, there are still a formidable amount of obstacles facing the decision. The exit process will take at least two years and will require authorization from numerous different countries and parliaments.